Shell Programming and Scripting

Somehow I can't get it for this basic bash problem. maybe someone can help.

What I try to do is:

a="world"
b="hello"

how can I move this into $c so that I can replace "helloworld" with "world hello" in sed like:

sed "s/\helloworld/ ${c}...

I tried several combinations but all with a wrong result:

c="${a};${b}"

echo $c;
hellod

You have not written what exactly you want in c. May be this works for you...

Code:

#!/bin/bash
a="world"
b="hello"
c=$a" "$b
echo $c

Thanx for the fast reply, but this does not work for me. I get the same result like in my example.

but I think I know why.
a="world"
b="hello"

a and b are lines randomly taken from a file, I think the problems come with the blancs in it:

a=$(perl -e 'srand; rand($.) < 1 && ($line = $_) while <>; print $line;' /text/part1.TXT)

if a line taken from part1.TXT is:
whatever line
I see this in the shell. I think a ' is missing somehow...

++ perl -e 'srand; rand($.) < 1 && ($line = $_) while <>; print $line;' /text/part1.TXT
' a='whatever line
+ ^
there is no ' at the end

try this

c=`echo "$a $b"`
echo $c

This works well if I set the variables like:

a="world"
b="hello"

but if I make this:
a=$(perl -e 'srand; rand($.) < 1 && ($line = $_) while <>; print $line;' /text/part1.TXT)

all things are messed up...

can it be that this randomly reading lines thing also carry linefeed or carriage returns with it, what I can't see but messes all tings up???

-----Post Update-----

booth solutions work perfect. thank you guys!

Ofcourse I should take care that the file format should be correct, if I play with text files in unix.

My files were in dos format, so everything I tried did not work... I converted to unix and all is allright now...